Estimation and evaluation of carbon sink of terraces measures in Loess Plateau : A Case Study of Wuqi County

Estimation and evaluation of carbon sink of terraces measures in Loess Plateau : A Case Study of Wuqi County Kaiyang Yu1, Xiaoping Zhang1, Hui Cheng2, Weinan Sun1, Wenliang Geng1, Haojia Wang1, Xuanhao Liu1, Liang He1, Yujie Zhang1, Zefeng An1, Yichen Wang1 1Institute of Soil and Water Conservation, Northwest A&F University, Yangling, Shaanxi 712100, China 2Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, China Abstract: Extensive terracing to cultivate land or plant trees and grasses, will affect biogeochemical processes in terrestrial ecosystem especially in areas with severe erosion. In order to clarify the carbon sequestration function and capacity of terrace in Loess Plateau, terraced fields with different planting types and years were selected to compare with corresponding slope land within Wuqi County (3,791 km2) of Loess Plateau to investigate the distribution characteristics of SOC on soil profile in 100 cm and searching for the influencing factors in the area. The results showed that：(1) Level terrace has significant carbon sink function in Loess Plateau. After the construction of terraced fields, SOC of six soil layers has the same variation trend with the construction years. The total SOC in the profile undergoes a rapid accumulation in the early 5-10 years of terracing construction, then exceeded the control group, and reaching a stable level after 20 years. (2) SOC in terrace dramatically decreases from surface layer to bottom layer, which exhibits surface aggregation effects. The content of SOC in 0-10 cm is significantly higher than that in deep soil layers, and the difference in SOC in deep soil is not significant. (3) The contents and accumulation rate of SOC in terrace are different with the planting types and years. Terraces with forest land generally has higher accumulating rate than other planting types. (4) There is significant correlation between total SOC and organic carbon content of large soil aggregates. Soil aggregates with particle size greater than 0.25mm determined the amount and trend of SOC content in the soil.  These results can provide an essential basis for improving the soil fertility and evaluating the benefit of terrace in carbon conservation on the Loess Plateau. Key words: Terrace; Soil organic carbon; Soil aggregate; Loess Plateau